Jul. 29, 2011

By Kaitlyn Gerber, Carleton College

Credit: NASA Goddard Space Center

An extensive new study by the University of Exeter has confirmed the warning that no one wants to hear: climate change is happening, and its effect on biodiversity could be devastating. Published in the Proceedings of the National Academy of Science (Vol. 108., no. 30), the study confirms that if the current trend of climate change continues, approximately one out of every ten species could face extinction by the year 2100.

These findings support the warnings of scientists around the globe that the Earth could very well be facing a sixth mass extinction event. For decades, scientists have noted that the current extinction rate is significantly higher than the historical rate, as indicated by the fossil record. In addition, climate scientists have often expressed worries that global warming will cause irreparable damage to biodiversity. This most recent study only confirms that these worries are justified.

Numerous prior studies have predicted the effects of climate change on a variety of species all over the world. The team at the University of Exeter set out to determine how accurate these predictions are based on documented changes that have already happened. To do so, they examined nearly 200 predictions climate change’s future effects, as well as 130 reports of changes that have already occurred. This study is the largest-ever review of such predictions.

The resulting paper confirms that the changes we are already seeing do, in fact, correlate with many of the predicted future impacts of global warming. The authors found that, on average, most climate change predictions are accurate. In fact, many of them are too cautious, not predicting the full extent of the changes that could occur.

Dr. Ilya Maclean, lead author of the paper, described the study in an interview as “a wake-up call for action.” In the paper, he stated that “the harmful effects of climate change are already happening and, if anything, exceed predictions.”

There are various examples of the already-existing effects of climate change. Rising temperatures, melting ice cover, changing patterns of rainfall, and the increasing acidity of the oceans are all indicators that global warming is causing harm to many species.

Global warming is thought to be particularly deadly to amphibians, who are particularly sensitive to climate change because of their permeable skin. In Yellowstone, droughts believed to be caused by global warming have caused severe declines in amphibious populations. Blotched tiger salamander populations fell by nearly half, while chorus frog populations fell by nearly 75 percent.

Emperor Penguins face the probability of a severe population decline if Antarctic sea ice declines as predicted.

Species vulnerable to climate change also include those who live in a narrow range of temperatures. The Bay checkerspot butterfly, which is federally threatened in the United States, is now locally extinct in several areas; it now only exists in several isolated pockets throughout the U.S. A 2002 study pointed out that as climate change increases in severity, more species will face extinction, as their habitat ranges will be diminished or permanently changed.

Melting ice at the poles also endangers some familiar species. Among them are different species of penguin, whose icy habitat is already shrinking. For the emperor penguins of Antarctica, past reductions in sea ice have yielded temporary population crashes, with recovery occurring only when the ice returned. If the ice were to melt permanently, as scientists fear, the penguins may disappear with it.

Marine species would be also be affected. Coral reefs, celebrated for the biodiversity that they hold, are extraordinarily sensitive to water temperature. When the water becomes too warm, the coral expels the symbiotic bacteria that it needs to survive, resulting in mass "bleaching" and eliminating the habitat that many species require. Although not all coral bleaching today is attributed to climate change - water that's too cold has a similar effect - global warming is predicted to cause a rise in sea temperatures. The resulting bleaching could cause devastating habitat loss, endangering many species that rely on reefs.

Coral bleaching, already a problem, will become much worse under the predicted influence of climate change.

These changes are only a few of the possible effects of climate change, yet they highlight the issue’s importance. The University of Exeter study serves to reinforce this point. If global warming continues at its current rate, we may face an extinction epidemic, where many now-familiar species will disappear.

“The impacts of climate change can be felt everywhere, and among all groups of animals and plants,” said Dr. Robert Wilson, co-author of the study, in an interview following the paper's publication. “We need to act now to prevent threatened species from becoming extinct. This means cutting carbon emissions and protecting species from other threats they face, such as habitat destruction and pollution.”

In other words, the only way to stop an impending extinction disaster is to act before it is too late.

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Kaitlyn Gerber will be a sophomore at Carleton College, where she plans to major in biology. Originally from Ridgefield, CT, she likes soccer, reading, and science, especially ecology and astronomy.